Abstract: Described are methods in which the retention times of a chromatographic column are adjusted through the control of the temperature of a mobile phase at the inlet to the chromatographic column. The temperature of the mobile phase at the inlet is different from the temperature of the chromatographic column. Adjustment of the temperature of the mobile phase at the inlet can be used as part of a method to transfer a chromatographic method from one liquid chromatography system to another liquid chromatography system. The method can alternatively be adapted for trapping a sample at the head of a chromatographic column to reduce the amount of band broadening of the sample from the sample injector of a liquid chromatography system. A gradient elution can then be performed to cause the concentrated volume of the analyte in the sample to elute in a tight band, resulting in improved measurement sensitivity.

Abstract: A device (100) for detecting a condition in a fluid system (14) and initiating a response based on the condition. The device consists of a sensor (12) that responds to a first and second condition of the fluid (13) in the system and a control means (10) that receives the responses and generates command signals in based on the received response. In a liquid chromatography system, the device is used to determine the volume of components of the fluid system. In addition, the device allow leaks to be detected and permits the fluid in the system to be transported at a optimum speed. The device is well implemented utilizing to a light emitter and light receptor that are sensitive to the fluid in either a gaseous or liquid state.